lighting: Electric Lighting Comes of Age

Electric Lighting Comes of Age

The first development in electric lighting was the arc lamp, which was evolved from the carbon-arc lamp demonstrated in 1801 by Sir Humphry Davy, in which an electric current bridges a gap between two carbon rods and forms a bright discharge called an arc. Early lamps of this type were made with an open arc; later ones were enclosed in glass and thus made more practicable. Carbon-arc street lamps, first produced by the American scientist Charles F. Brush, were used in Cleveland in 1879 and soon came into wide use in other cities. The mercury-vapor electric lamp was devised by the American inventor Peter Cooper Hewitt in 1903. This type of lamp makes use of a pool of mercury liquid in a condition of high vacuum; when an electric current passes through the mercury it produces ionized vapor, which gives off a blue-green light. Modern improvements have given this lamp a much greater efficiency. The neon lamp, developed by the French physicist Georges Claude in 1911, has been largely used in commercial signs.

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